1. Field of the Invention
The present invention relates to a method for manufacturing an SOI (silicon on insulator) substrate and a method for manufacturing a semiconductor device.
2. Description of the Related Art
In recent years, integrated circuits using an SOI (silicon on insulator) substrate in which a thin single crystal semiconductor film is formed on its insulating surface, instead of a bulk silicon wafer, have been developed. Since parasitic capacitance between a drain of a transistor and a substrate is reduced with use of the SOI substrate, the SOI substrate has been attracted attention as a substrate which improves performance of semiconductor integrated circuits.
Smart Cut (registered trademark) method is known as one of methods for manufacturing an SOI substrate (for example, see Patent Document 1: Japanese Published Patent Application No. 2000-124092). An outline of a method for manufacturing an SOI substrate by Smart Cut (registered trademark) method is described below. First, by an ion implantation method, hydrogen ions are added into a silicon wafer which serves as a separation substrate to form an ion added layer at a predetermined depth from the surface. Then, the silicon wafer into which the hydrogen ions are added is bonded to another silicon wafer (a silicon wafer to be separated) with a silicon oxide film interposed therebetween. After that, by heat treatment, the ion added layer serves as a cleavage plane, and the separation silicon wafer into which the hydrogen ions have been added is separated as a thin film, whereby a single crystal silicon film can be formed over the silicon wafer to be separated to which the separation silicon wafer has been bonded. Smart Cut (registered trademark) method is also referred to as a “hydrogen ion implantation separation method”.
A method in which a single crystal silicon layer is formed over a supporting substrate made of glass by such Smart Cut (registered trademark) method has been proposed (for example, see Patent Document 2: Japanese Published Patent Application No. H11-163363).
In addition, a method for reusing a silicon wafer which is a separation substrate by polishing of the silicon wafer after cleavage in Smart Cut (registered trademark) method has been proposed (for example, see Patent Document 3: Japanese Published Patent Application No. 2007-251129).